[DeathSheep]

First off, I REALLY appreciate your advice. I've learned a ton just reading your responses.

That said, that code doesn't seem to be working either. I'm still getting a list of random things that aren't the damage types I specified in the dropdown. I'm really baffled. Here is the code as it stands now:

  <thing id="cBerPRDewbInst" name="Dewback's Instinct" description="Choose three damage types other than true damage. While raging, you have resistance to the chosen damage types." compset="CustomSpec" uniqueness="unique">
    <fieldval field="usrCandid1" value="component.DamageType & (thingid.dtAcid|thingid.dtCold|thingid.dtFire|thingid.dtPRForce|thinid.dtPRIon||thingid.dtLightning|thingid.dtNecrotic|thingid.dtPoison|thingid.dtPsychic|thingid.dtPRSonic) & !Helper.Helper"/>
    <fieldval field="usrCandid2" value="component.DamageType & (thingid.dtAcid|thingid.dtCold|thingid.dtFire|thingid.dtPRForce|thinid.dtPRIon||thingid.dtLightning|thingid.dtNecrotic|thingid.dtPoison|thingid.dtPsychic|thingid.dtPRSonic) & !Helper.Helper"/>
    <fieldval field="usrCandid3" value="component.DamageType & (thingid.dtAcid|thingid.dtCold|thingid.dtFire|thingid.dtPRForce|thinid.dtPRIon||thingid.dtLightning|thingid.dtNecrotic|thingid.dtPoison|thingid.dtPsychic|thingid.dtPRSonic) & !Helper.Helper"/>
    <tag group="Helper" tag="Primary"/>
    <tag group="abCategory" tag="BersInstinct"/>
    <tag group="abRange" tag="Personal"/>
    <tag group="abDuration" tag="ConstRage"/>
    <tag group="SpecSource" tag="cHelpBrs"/>
    <tag group="Helper" tag="Helper"/>
    <tag group="Helper" tag="Free"/>
    <eval phase="First" index="3"><![CDATA[
       doneif (hero.tagis[Hero.Raging] = 0)

       doneif (tagis[Helper.Disable] <> 0)

      ~ If nothing chosen then get out now!
      doneif (field[usrChosen1].ischosen = 0)
      doneif (field[usrChosen2].ischosen = 0)
      doneif (field[usrChosen3].ischosen = 0)

       ~ Collect selected types of damage and pull the Resistance tags from them.
      perform field[usrChosen1].chosen.pulltags[DamageRes.?]
      perform field[usrChosen2].chosen.pulltags[DamageRes.?]
      perform field[usrChosen3].chosen.pulltags[DamageRes.?]

      perform hero.pushtags[DamageRes.?]]]></eval>
    </thing>

I tried taking the third choice out in case that was giving the compiler a nervous breakdown, but nothing changed.